* doc/tm.texi (defmac SMALL_REGISTER_CLASSES): Remove.
(TARGET_SMALL_REGISTER_CLASSES_FOR_MODE_P): Add documentation,
based on the above, for new target hook.
* config/sh/sh.h: Replace SMALL_REGISTER_CLASSES with new target
hook definition.
* config/sh/sh.c (sh_small_register_classes_for_mode_p): Add
implementation of the hook that considers all register classes
small except for SH64.
(sh_override_options): Use the new hook.
* config/sh/sh-protos.h (sh_small_register_classes_for_mode_p):
Add prototype.
* config/arm/arm.h: Replace SMALL_REGISTER_CLASSES with new target
hook definition.
* config/arm/arm.c (arm_small_register_classes_for_mode_p): Add
implementation of the hook that considers all register classes
small for THUMB1.
* config/arm/arm-protos.h (arm_small_register_classes_for_mode_p):
Add prototype.
* config/mips/mips.h: Replace SMALL_REGISTER_CLASSES with new target
hook definition.
* config/mips/mips.c (mips_small_register_classes_for_mode_p): Add
implementation of the hook that considers all register classes
small for MIPS16.
* config/mips/mips-protos.h (mips_small_register_classes_for_mode_p):
Add prototype.